ESTRO 2023 - Abstract Book

S683

Monday 15 May 2023

ESTRO 2023

Hadrontherapy,Clinical Bioengineering Unit, Clinical Department, Milano, Pavia, Italy; 8 CNAO National Center for Oncological Hadrontherapy , Scientific Direction, Pavia, Italy Purpose or Objective To analyze the real-world data set of the recurrent/refractory ovarian/salpinx cancer (RR-OSC) treated with carbon ion radiotherapy (CIRT) at QST (Japan) and CNAO (Italy). Materials and Methods CIRT for RR-OSC commenced in 2006 at QST and in 2019 at CNAO. The endpoints of this preliminary analysis were the rate of objective response (OR) to CIRT, 1 and 2-years local control (LC) rates and acute/late toxicities. OR was defined as the sum of complete response (CR) and partial response (PR). According to centre policy, toxicity was scored using RTOG/EORTC and CTCAE scales. Actuarial outcomes were evaluated using the Kaplan-Meier method and the impact of dose (>/ ≤ 52.8 Gy[RBE]), age (>/ ≤ 60 years), tumor site (lymph node/parenchymal), ethnicity (Asian/Caucasian) on LC survival using log- rank test/multivariable Cox regression analysis. Univariable logistic regression was employed to assess the statistically significant parameters’ relationship with OR ( α =0.05). Results A total of 26 women (58% Asian and 42% Caucasian) underwent CIRT for RR-OSC. All patients completed the treatment. 21 patients were radiotherapy naïve, while 5 patients received a previous photon beam treatment. The median age at CIRT was 59.5 years (range:44-81) and the most common histological type was high-grade serous carcinoma (42%). All patients underwent at least 1 cytoreductive surgery and at least 1 previous line of chemotherapy. The median total dose prescription was 52.8 Gy[RBE] (range:39-64 Gy[RBE]). No concomitant systemic therapies were administered during CIRT; PARP-I and anti-VEGF were stopped before CIRT. Lymph node lesions accounted for 54% (N=14), followed by parenchymal ones (abdominal=7;pelvic=4,brain=1, for a total of 46%). Eleven (42%) patients achieved CR within 6 months after CIRT. With a median follow-up of 13 months, the OR was 85% and only 4 (15%) patients had an in-field local recurrence. The median LC was 12 months (range 2-193), and the 1- and 2-year LC rates were 89% and 74% respectively. Total dose (p=0.63), age (p=0.35), CIRT site (p=0.46) and ethnicity (p=0.68) were not significantly associated with LC. These items were not related to OR either. Only one case of G3 EORTC/RTOG enterocolitis in the acute and late phases was observed. No G ≥ 3 toxicities were recorded in re-irradiated patients. Six patients received PARP-i and 4 anti-VEGF, which seemed not to exacerbate the risk of severe toxicities. Conclusion Our real-world data showed for the first time the efficacy and safety of CIRT in patients with RR-OSC, even in the case of re-irradiation. Considering its dosimetric and radiobiological advantages, CIRT might be a therapeutic option for RR-OSC, with the aim also to delay a new chemotherapy line. Prospective and randomized studies are warranted. PD-0811 Image-guided Stereotactic Body Radiotherapy for intermediate and high-risk endometrial carcinoma M.I. Antunes 1 , S. Vieira 1 , A. Soares 1 , A. Rocha 1 , E. Freitas 1 , J. Stroom 1 , C. Greco 1 1 Champalimaud Foundation, Radiotherapy, Lisbon, Portugal Purpose or Objective To evaluate the feasibility of adjuvant image-guided Stereotactic Body Radiotherapy to the vaginal cuff (VC-SBRT) for intermediate and high-risk endometrial carcinoma (EC). Materials and Methods Between February 2018 and November 2020, stage I to III EC patients who underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy with pelvic +/- paraaortic nodal sampling were treated in an institutional review board- approved study. The aim of the study was to reproduce adjuvant High Dose Rate (HDR) brachytherapy dose distributions with VC-SBRT. Patients were submitted to SBRT +/- External Beam RT (EBRT) according to risk classification. Those with lower risk of relapse (Group 1) underwent VC-SBRT alone (21Gy in 3 fractions), whereas higher risk patients (Group 2) were treated with EBRT (46Gy/23 fractions) plus VC-SBRT (15Gy/2 fractions). For both groups the vaginal cuff was treated to 100% of prescribed dose at a depth of 5 mm from the mucosa surface (vc) and to 150% to the mucosa surface (vcm). Both Pelvic EBRT and SBRT boost were treated using VMAT. The PTV boost was obtained from the CTV using an expansion margin of 3mm. Boost patient setup is shown in figure 1. Dose volume constraints for organs at risk (OARs) were defined according to the Gyn GEC ESTRO Recommendations. Clinical evaluation was performed within 2 weeks after completion of SBRT, at 3 and 6 months, then every 6 months until the end of year 3, then annually. Toxicity evaluation was recorded according to Common Toxicity Criteria (version 2.0) (CTCAE) scores. Estimated overall survival (OS) and disease-free survival (DFS) were calculated using Kaplan Meyer survival curves.